Delaminations Onset and Propagation for CFRP Angle Ply Laminates under Uniaxial Fatigue Loads

Abstract

Delamination is a failure mode particular to composite materials and it is introduced by the interlaminar components of the stress tensor. Under static uniaxial loading, a 3D stress state occurs at the free edges of a composite structural member whereas the values of the interlaminar stress components can become critical and determine the static failure of such member. The purpose of this paper is to assess and determine the influence of the interlaminar stresses on the failure of unnotched angle ply CFRP laminate specimens subjected to tension-tension uniaxial fatigue loading. This study is composed of two parts, namely: (1) a numerical analysis to determine the 3D stress state in the composite laminate under static loading with the purpose to identify the points where the interlaminar stresses are critical and delaminations are expected; (2) an experimental analysis, based on tension static and fatigue T-T tests, to evaluate if delaminations occur at the same points as those identified during the numerical analysis and if their propagation produces the final fatigue failure at an external maximum load equal to 50% of the ultimate static failure load.